Sterilizer



June 13, 19 33. 5 c, s o 1,914,334

STERILIZER Original Filed April 14, 1927 2 Sheets-Sheet l June 13, 1933.Q Q STQDDARD 1,914,334

STERILIZER Original Filed April 14. 1927 2 Sheets-Sheet 2 26 MIN.

TEMPERATURE -DEGRES F a a x I l0 A 3.5 4f Maw/rasagave gy y AfrdkMS'KS'.

Patented June 13, 1933 UNITED STATES PATENT OFFICE GEORGE C. STODDARD,OF BUBLINGAME, CALIFORNIA, ASSIGNOR TO THE DE LAVAL SEPARATOR- COMPANY,OF NEW YORK, N. Y., A CORPORATION OF NEW JERSEY STERILIZER Originalapplication filed April 14, 1927, Serial No. 183,890. Divided and thisapplication filed April 8,

1930. Serial It is known to heat water in a vessel, such as asterilizer, by immersing therein an electric heating element. It isalsoknown to heat the water in a separate casing that contains the heatingelement and through which a 011'- culation of water is established fromand back to the vessel. It is necessary to heat the water to a certaintemperature and to hold it at or above that temperature for a minimumpredetermined time in order to insure thorough sterilization. Itrequires careful watching to insure that the desired temperature isreached and maintained. With the cover of the sterilizing vesselapplied, a too prolonged application of heat will injure, and maydestroy, the heating .element. It has been found practicable to controlthe temperature thermostatically, but ordinary thermostatic control isineffective to limit the duration of the application of heat. Anunnecessarily prolonged appiication of heat involves serious waste ofcurrent, even though the temperature may be automatically controlled.

The object of my invention is to avoid the necessity of carefulwatching, insure that the desired temperature shall be maintained abovea desired minimum temperature for a predetermined time, and avoidoverheating, waste of current and danger of damage to the heaterelement.

A preferred embodiment of my improved sterilizing apparatus is shown inthe accompanying drawings, in which- Fig. 1 is a vertical sectional viewof a sterilizer, the upper cover part not being completely shown.

Fig. 2 is a vertical sect-ion through the thermostatic control box.

Fig. 3 is a diagram illustrative of the operation.

The sterilizer vessel w, provided with a cover a which is foreshortenedin its vertical dimension, is provided in its bottom with a groove 5having an inclined bottom so that it is relatively deep at one end andgradually diminishes in depth toward the other end. For example, thegroove may be 6 or 7 inches wide and of a maximum depth of three inchesat fine end and taper to nothing at the other on Outside and below andspaced from the vessel a, and preferably inclined and extending parallelto, and immediately below, the bottom of the groove, is a casing dcontaining an electrical heating element 0. The opposite ends of thecasing d are provided with two flanged nipples e and f by means of whichcasing d is secured to the bottom of vessel a.

Nipple e, at the lower end of easing d, communicates with the interiorof vessel a at the deep end of groove 6. Nipple f, at the higher end ofcasing d, extends through the bottom of the shallow end of groove 1) andsupports the L end of a perforated pipe 9, which extends, preferably ina horizontal direction, along and immediately above groove 6. A drainplug and nipple It extends from the lowest end of casing d, and collectsdirt and sediment which may settle by gravity at this end.

In an enclosed box 2', above the head of heating element 0, is placed athermostat of the diaphragm expansion type. The thermostat comprisesswitch contacts 777. and n connected electrically with element 0. One ofthe contacts m is fixed and the other n is on the end of a lever 0.Lever 0 carries a threaded rod 7", which, normally, nearly touches adiaphragm p, which, when it expands, engages rod 7" and thereby actuateslever o. Diaphragm 79 is hollow and contains ethyl alcohol or othersuitable liquid convertible into a vapor at a low temperature. Itexpands when a certain temperature (say 205-209 degrees F.) is reachedwithin vessel a and in the movement of its expansible wall swings lever0 on its pivot and retracts contact n from contact m, thereby openingthe circuit to heating element 03. Lever 0 carries at its other end atrip hook or trigger t havmg a notch which, when the lever is swung asdescribed, engages a fixed pin 8 and holds lever 0 from returning afterthe temperature drops below the temperature at which the diaphragm isheld expanded. By means of the hand-operable rod 4;, the switchmechanism may be reset.

The hot water and steam surge through the heater element in the courseindicated by the arrows and are discharged through the perforations inpipe g. It is found decidedly advantageous to enclose the heatingelement in a casing separate from the sterilizer vessel and ofrestricted size rather than to immerse it in a trough in the bottom ofthe sterilizer vessel. In the latter case, the water must actually boilbefore the temperature in the sterilizer will rise to the desireddegree, whereas in the construction shown, steam can be generated anddelivered in a comparatively short time, say 30 or 35 seconds.

It is always advisable, and in some States the law requires, that thetemperature shall remain above a given temperature, say 170 degrees F.,for a given time, say fifteen minutes. It is diliicult and unnecessary,and moreover undesirable, to hold the temperature stationary at ustabove the minimum for a predetermined time. In my invention, the desiredresult is produced by allowing the fluid to heat up to above the desiredminimum and then cut oil the application of heatand allow it to drop tothe desired minimum; the maximum degree of heat being such that the timerequired to heat from minimum to maximum and cool down from maximum tominimum will equal or exceed the minimum time to which the fluid is tobe heated above the minimum. The thermostatic control herein describedaffords a ready means for insuring such operation automatically.

The operation of the sterilizer comprises the following cycle ofoperations:

It the operator desires to secure hot water for washing, any desiredquantity of water is run into vessel 01.

The electric circuit to heater 0 is then closed and is maintained closeduntil the water is at the desired temperature. It the operator shouldfail to open the circuit, the thermostatic control will efiect theopening, and, if the cover is on, will act to save element 0 frominjury.

After the circuit is opened, the desired amount of hot water is removed,leaving in the vessel the amount desired for the sterilizing operation.

The milk cans, or other articles to be sterilized, are then placed inthe sterilizer and the cover put on.

The current is then again turned on. The temperature inside vessel arises to the predetermined point (say 200 to 210 degrees F.) at whichthe diaphragm p suddenly expands, which swings lever 0, opens the switchm, a, and engages trip hook at with pin 8 and holds the switch open.

The temperature within the vessel then drops.

Not only does the thermostatic control protect. the heater element andinsure that the articles to be sterilized shall be subjected to atemperature above a predetermined minimum for a predetermined time, butit avoids waste of current.

The apparatus above described is especially adapted to so control theapplication of heat as to secure certain important advantages, otherthan those hereinbefore enumerated, which are not at once apparent.Thus, the temperature of the room in which the sterilizing process takesplace may vary with in wide limits. It is uneconomical to insulate thevessel. It is obvious that with a warm external atmosphere, thetemperature will rise more rapidly and fall more slowly, than with acold external atmosphere. It has been found that, in the operation of myinvention, the elapsed time between the rise and the return to minimumtemperature will be about the same regardless of external temperatureconditions. In Fig. 3 plotted curves illustrate such comparativeoperations; curve a: showing the elapsed time above a minimumtemperature under conditions of comparatively slow heat radiation andcurve fl showing the elapsed time above a minimum temperature underconditions of rapid heat radiation.

It has also been experimentally shown that this desirably fixed factorvaries but little whether or not articles to be sterilized are placedwithin the vessel. Experiment seems to show that with no load theduration of efl'ective sterilizing conditions is slightly less than withload. However, the variation is so slight under all imaginable vari-,

able conditions that it is only necessary to provide, under anyconditions, for the maintenance of sterilizing temperatures for asomewhat longer time than the required minimum, and it is thereby madecertain that, this time will not fall below the required min imum underany other condition.

The new method, herein described. of heating articles to be sterilizedand which, by the use of the improved sterilizing apparatus hereindescribed and claimed, is carried out with maximum efliciency, forms thesubjectmat-ter of another application, filed April 14, 1927, Serial No.183,890, of which this application is a division.

Having now fully described my invention, what I claim and desire toprotect by Letters Patent is:

1. In a sterilizer, the combination with a sterilizer vessel, of acasing outside the vessel, an electric heater element within the casing,means providing for fluid circulation from the interior of the vesselthrough the casing and thence back to the interior of the vessel, aswitch for opening and closing the circuit to the heater element, adiaphragm in operative relation with a fluid which is in l quid phasebelow, and in vapor phase above, a given temperature, said diaphragmbeing operable upon the conversion of liquid into vapor to open theswitch and tending to operate to close the switch when said vapor isreconverted to a liquid, and means operating automatically to hold theswitch open when it is opened by the diaphragm and which is manuallyreleasable to allow the diaphragm to close the switch when the containedfluid is in liquid phase.

2. In a sterilizer, the combination, with a sterilizer vessel, of acasing outside the vessel, an electric heater element within the casing,means providing for fluid circulation from the interior of the vesselthrough the casing and thence back to the interior of the vessel, aswitch for opening and closing the circuit to the heater element, adiphragm, temperature-controlled means adapted, when the temperaturewithin the vessel rises to a predetermined degree, to actuate thediaphragm, means operable by the so actuated diaphragm to open theswitch, and manually releasable means adapted to hold the switch in openposition during the fall of temperature succeeding the opening of theswitch.

3. In a sterilizer, the combination with a sterilizer vessel adapted tocontain fluid and articles to be sterilized, of an electrically operatedelement for heating the fluid to raise the temperature within the vesselsubstantially above the desired minimum temperature of sterilization, anelectric circuit connected with said element, a thermostaticallycontrolled device, a switch for opening and closing said circuit, aconnection between said thermostatic element and said switch wherebysaid switch is positively opened and closed by said thermostaticelement, and manually releasable means adapted to hold the switch openand prevent the same being closed by the thermostatic element until saidmeans is manually released.

4. In a sterilizer, the combination with a sterilizer vessel, of acasing outside the vessel, an electric heater element within the casing,means providing for fluid circulation from the interior of the vesselthrough the casing and thence back to the interior of the vessel, aswitch lever for opening and closing the circuitto the heater element, adiaphragm in operative relation with a liquid which is convertible intoa gas at a given temperature, said diaphragm being actuable, when saidliquid is so converted into a gas, to open the switch lever, a pin, atrigger carried by the switch lever and adapted, in the opening movementof the switch lever, to engage said pin and hold the switch lever in anopen position, and manually operable means to disengage the trigger andpin.

In testimony of which invention, I have hereunto set my hand, at SanFrancisco, Calif., on this 29th day of March, 1930.

GEORGE C. STODDARD.

